1. Field of the Invention
This invention relates generally to a vibration reduction system for reducing structural vibrations and noise, and more particularly, to a system and method that uses impedance regulated active mounts.
2. Description of the Related Art
A variety of systems have been proposed and implemented for reducing noise and vibration acting on structures. In a typical structural-acoustic system, an excitation energy or disturbance is generated in a structure. This disturbed structure will be referred to as a deck. A deck is a platform for any type of disturbance-creating machine or machines including, but not limited to turbines, generators, pumps, and motors. This deck is attached to a second structure at a finite number of discrete locations. The deck typically transmits vibratory energy and noise to the second structure through these discrete attachments. This secondary structure will be referred to as a hull. The hull is any base or foundation upon which a deck is mounted.
Conventionally, passive mounts are placed at locations between the hull and deck in order to reduce vibratory energy transmission from the deck onto the hull. Usually several mounts are used, depending on the specific installation requirements. Passive mounts reduce vibration transmission by acting as simple springs.
Passive mounts suffer from a number of limitations. For example, proper performance of passive mounts are limited to low frequency applications. Wherein, at high frequencies passive mounts degrade and become wave bearing, thus losing their simple spring like characteristics.
In an attempt to overcome the deficiencies of passive mounts, it has been proposed to position active mounts throughout a system to actively control the noise and vibration of the system. These active mounts typically include a controllable actuator which reduces system vibration or noise by introducing a canceling vibration to the system. The ability to effectively reduce the vibration or noise of a system by the use of active mounts, however, is often limited by the coupling which occurs between the active mounts. Generally, "coupling" describes the effect an actuation of one active mount has on the other active mounts of the same system. As a result, current control of active mounts requires a complex system which attempts to take into account the detrimental mount coupling.